Conventionally, there are image reading apparatuses capable of reading an original in two different ways, i.e., reading an original stationarily placed on a platen glass by moving a scanner (referred to as “stationary reading operation” hereinafter), and reading an original by a scanner at a fixed position while feeding the original along the platen glass by an automatic document feeder (referred to as “read-while-feed operation” hereinafter) are known. This read-while-feed operation can shorten the reading time of entire originals as compared to the stationary reading method because original exchange and reading can be simultaneously performed, and the image reading section need not be returned to the home position to read the next original.
In the above-described read-while-feed operation, however, since an original image is read at a fixed position on the platen glass, black streaks may be formed on the read image due to dust or dirt between the platen glass and the original or on the lower surface of the platen glass, and an original image can not be read properly.